Sacha Guitry is not a movie director, let alone a screenwriter. Guitry claims so in the opening credits sequence: "I daresay this is stage play." As for me this kind of heavy-handed foreword is out of place in a movie. "L'auteur, bien entendu" shows off and introduce us to the whole cast starting with a grand praise of Michel Simon. The monologue is good but Guitry is insufferably pedantic while we're supposed to get in the movie. Yet I admit this clunky device worked for Le Roman d'un tricheur, but only because 1/Guitry was the lead 2/he played a lifelong cheat and 3/he told us his life in a series of flashbacks.
Now La Poison would have been really poor indeed were it not for Michel Simon's talent. Once Sacha Guitry lets the movie start it rolls up pretty good. The satirical tone tends to be heavy but with Michel Simon playing at times borderline dramatic that sets a good balance... until the movie gets clunky again. Michel Simon has a very good scene with his presumptive lawyer followed by an awfully serious one involving the lawyer and the visiting general attorney. There you can see that the movie needs Michel Simon as a driving force (and Germaine Reuver as the main resulting force of course) : that's a very low and overstretched point made just before the climax. The Climax: Guitry shoots it quite on the nose but the scene is so meaningful it doesn't require much more.
The problem is after the climax the movie has nowhere to go. The satirical tone? It was good enough for the setup but it keeps playing like it's a light comedy (I'm sorry but satirical tone + murder doesn't necessarily make a dark comedy). So the people from the village keep playing the regular types they were assigned to and the trial is totally farcical. There you can only regret that the lawyer's part had been so blatantly undersized. As for Michel Simon if you let him become too strong a character he will overshadow everyone in the scene. And that's what happens: from the climax down to its end La Poison errs and cannot make up for Guitry's poor cinematographic vision.
